Differential pressure flow rate measurement device



1954 H. J. VELTEN ETAL 2,687,645

ENT DEVICE DIFFERENTIAL PRESSURE FLOW RATE MEASUREM 2 Sheets-Sheet 1 Filed March 2, 1950 FIG.

E LTEN HERBERT ZIEBOLZ JNVENTORS V T R E B U H ATTORNEYS 1954 H. J. VELTEN ETAL 2,687,645

DIFFERENTIAL PRESSURE FLOW RATE MEASUREMENT DEVICE Filed March 2, 1950 2 Sheets-Sheet 2 HUBERT J. VE LTEN HERBERT ZIEBOLZ INVENTORS ATTORNEYS UNITED STATES PATENT OFFICE DIFFERENTIAL PRESSURE FLOW RATE MEASUREMENT DEVICE Hubert J. Velten, Homewood, and Herbert Ziebolz, Chicago, Ill., assignors to Askania Regulator Company, Chicago, 11]., a corporation of Illinois Application March 2, 1950, Serial No. 147,188

3 Claims. (01. 73 211) l The present invention relates to flow rate measthe supposed necessity of supporting the bafile urement and particularly to structure arranged plate on reaches of signal pipe extending axially fiow in the path. obstruction in the flow path or to an elbow of More specifically, the invention relates to imthe conduit to permit the axial disposition of provement of structure for providing a specialbafiie plate-supporting signal pipes.

ized form of restriction orifice of a type that has The present invention avoids these various unpath tend to disturb the smoothly flowing charrectly from the surrounding conduit wall and actor of fluid stream and thereby prevent develindependently of the signal pipes The arrangeopment of a steady pressure drop across a conment thereby is such as to be readily insertable ventional center orifice restriction that continuor withdrawable from between meeting ends of flowing stream, and surrounded by an annular baffle plate centrally disposed in a w p h for orifice between itself and the path-enclosing wall, developing regions of steaoy pressures the difwhen disposed in a region of flow conditions that ference between which accurate y measures volcreate such stream disturbance as to iender useume flow iate, are not materially affected by the less for flow measurement the conventional cenpresence of radial supporting structure extended ter opening orifice, creates adjacent its opposite across the annular orifice defined by such plate,

measurement of differential between pressures of A primary object of the invention is the provisuch regions. sion of a novel flow-restricting orifice-forming The arrangement heretofore proposed for orifies-forming structures of this kind has involved a central region of a fiuid flow path and substanwhich extend respectively from the point of plate 40 structure projecting inward from the surrounding location up and downstream substantial distances flow path-enclosing conduit wall.

to points of support from the conduit wall at Another bj is t provision o a novel aswhich they enter the interior of the fiow-enclossembly arrangement in a flow pa h n l by a mg conduit The signal ipes in such arrangec l f stru ur pr vidin a n r lly disment have been provided, adjacent their battle p e a fi plate d nal pipes h v D plate-supporti'ng ends and within the steady pres- Sure-admitting Openings Closely j cent the sure regions adjacent the bafile plate surfaces, baffle plate Surfacesth pressure-adm1tt1ng ports Arrangements of Still another object is the provision of such an this kind, while affording satisfactory orifice per- Prime-firming Structure, Whereln the heme plate formance, has proven extremely inconvenient in readily replaceable by bame plates of other the region of the orifice structure. Additionally, which is such as to permit ready formation of the orifice-defining margins with bevels, to provide accurate definition of the effective orifice area by sharp edges and downstream tapering away from the flowing stream of the marginal surfaces forming such edges to prevent exertion on the stream of friction effects that have been found to destroy the calculated effiect of the orifice area.

In the accompanying drawings:

Fig. i is a median sectional view through part of a conduit line that encloses a fiow path, wherein is mounted a diiferential pressure-developing and detecting assembly arranged in accordance with the invention.

Fig. 2 is a plan of an orifice-forming structure arranged in accordance with the invention.

Figs. 3 and a respectively are fragmentary median sectional views showing various signal pipe arrangements that may be used with orificeforming structures arranged in accordance with the invention.

Fig. 5 is a sectional view similar to Fig. 1, showing a more highly developed .orifice forming structural arrangement.

Fig. 6 is a plan .of the downstream side .of a structure of the arrangement shown by Fig. 5.

Fig. 7 is an enlarged fragmentary view of such a structure.

Fig. 8 is a sectional view, corresponding to a section on line 8-8 of Fig. -6 but showing a slightly modified form of the arrangement.

Describing the drawings in detail, and first referring to the more general form of the invention disclosed by Figs. 1 to 4, in Fig. l the conduit line is is to be considered as so arranged as to produce a disturbed flow condition in a region wherein it is desirable measure flow rate by a flow-restricting orifice. The elbow l i shown in the conduit line is a typical flow-disturbing condition, creating regions of disturbance extending considerable distances both up and downstream, and of such character .as to preclude development of a steady and measurable pressure difierential across a flow-restricting orifice of conventional center opening type. Other conditions creating similar ,fiow disturba-nce zones are entrance and exit ends of flow path-enclosing conduit lines, branches, and .obstructions in the conduit lines. Experiment and use has demonstrated conclusively that, as set forth above, orifice-forming structures .of the centrally disposed bafiie plate type here involved are capable of developing steady upstream and downstream pressures, .diiferential between which substantially of the flows producing them, as in the case of more conventional orifice structures arranged in regions of ideal stream flow.

The orifice-forming structure of the present invention is preferab fiat and relatively thin to permit ready insertion between and withdrawal from between adjacent ends of successive sections of the conduit line enclosing the flow path. As shown in Fig. i, the orifice plate i2 is secured between flanges 13 at the ends of adjacent sections of the conduit line, the sections being secured together in any conventional manner.

Referring to Fig. 2, plate 12 comprises a mar ginal portion 55 for engagement between adjacent .conduit section lends. A central sbafile plate part 56 is spaced inward from marginal part M3 by a series of orifice-forming openings 11, shown as arcuate and together defining an annular orifice surrounding baffle plate part 16 are proportional to second powers l ii substantially completely, but interrupted by narrow web parts iii of the plate, such web parts being attached at their opposite ends to the marginal and baille plate parts l5, 15.

Again referring to Fig. 1, baffie plate part 15, supported centrally of and transverse to the fiow path enclosed by conduit line [0, forms regions of steady pressure at its upstream and downstream sides. The extent and shape of these regions depend somewhat on the size and shape of the baffle plate portion it and the size and shape of the orifice-forming openings ll, as well as on the volume rate of flow through such openings, but they appear to extend in L somewhat conically tapering form from the margin of the baffle plate to substantial distances up and down stream in the general shape indicated by the dotted lines l9.

Signal pipes for transmitting pressures of the regions of steady pressure indicated by lines iii may be arranged in a variety of ways, as will appear from the following. 'In Figs. 1, 3 and 4, such pipes 2c are shown as extended substan! tially axial .of the fiow path from points .of support located substantial distances from the plate structure. These pipes ter' iate within the regions of steady pressure developed on op posite sides of the baffle plate part be of the assembly, which are indicated by lines 18. Preferably the ends of signal pipes :28 are closely adjacent but out of actual contact with the plate structure. They are provided with pressure-admitting openings which may be arranged in a variety of ways so long as they are disposed within the steady pressure regions. In Fig. i the pressure-admitting openings are shown as simple ports '2! distributed axially and .circume ferentially of the end regions .of pipes :21]. in Fig. :3 they are shown as stub taps 2'2, and Fig. 4 they comprise open ends 25 of pipes 2i) themselves.

It is standard practice in flow-measurement by differential pressure developed across va flow.- restricting orifice, to bevel the orifice-defining margin .of the structure, providing .a sharp edge that is disposed .on the upstream side .of the mounted assembly, the marginal surfac downstream of such sharp edge being inclined away from the constricted stream flowing through the orifice. This arrangement permits accurate se lection of the magnitude range of pressure dife ferential developed by volume fiow rates in a given range. Not only does the sharp edge permit more exact .selection of the minimum crosssectional orifice area that it defines, but it also renders such area the effective area of the .orifice by substantially eliminating the friction of feet .upon the stream .of marginal parts that are in or approach parallel relation to the direction of flow through the orifice. Such friction effects are difficult if not impossible to predict or select.

Figs. 5 to .8 disclose .an embodiment pf the invention that includes provision for ready eccompli hment of this highly desirable beveling, and also for the desirable additional feature of repiaceability of the battle plate that develops, th steady pressure regions in disturbed stream fiows and develops a d-ifierential between the p sures of such region .Bepla ement of the baffle plate of a given installation is desirable ior changing the orifice area, for measu ing :fiOW rate ranges of difierent magnitudes occurring at different times .or .during different types of, operation.

As shown in Figs. 5 to 8, the orifice-forming sive conduit sections, as the flanges 2'! of Fig. 5, and surrounding a series of orifice-forming open- Advantageously this center part 3| isi formed integral with the annular marginal part 26 and the Dowel pins 33 tioning the baffle plate 30 on the spider, it bedisposition in the and a trailing surface 36 mounted assembly, that tapers web side edges fully to the nular outer portion 26, the

since the webs and their side surfaces are masked by the baffle plate.

downstream surfaces of 8 the baflie plate Fig. 5 discloses a slight modification of the signal pipe arrangement. In such arrangement the signal pipes 42 ily replaceable orifice-defining member for selection of effective orifice cross-sectional area, but additionally provides From the foregoing, the basic concepts of the invention will readily be apparent, and it will be the invention as defined by the appended claims.

We claim:

of said preselected percentage and comprising the sole attachment of said bafile plate to said conduit line; and a pair of signal pipes positioned by the conduit line independently of said structure, said pipes projecting inward from the Wall of said conduit line, respectively extending into the different said regions of stable pressures upon opposite sides of said baffle plate, and the inner ends of said pipes being closely adjaeent to but free of said structure and spaced apart to permit the latter to be withdrawn radially from between them while they remain positioned by said wall, and said pipes having pressure-admitting openings to their interiors located within the bounds of said baflie plate periphery, in said stable pressure regions and inwardly pa ed from said conduit line wall.

2. A differential pressure-developing and detesting assembly arranged in accordance with claim 1, wherein said marginal portion is engaged between the ends of adjacent .conduit sections, and said marginal portion and web means have opposite corresponding flat surfaces that are coplanar.

of said baifie plate.

References, Cited the file of this patent UNITED STATES PATENTS Number Name Date 2,210,448 Dodge Aug. '6, 1940 2,259,014 Upperman Oct. 14, 1941 2,306,940 Fischer -7 Dec. 29, 1942 FOREIGN PATENTS Number Country Date 578,873 Germany June 19, 1933 

